In general, a troffer is a rectangular light fixture configured to fit into a modular dropped ceiling grid (for example, a two-foot by two-foot space, or a two-foot by four-foot space), and typical designs accommodate standard-size fluorescent lamps (such as T12, T8 or T5 bulbs). A waveguide troffer is a ceiling mounted luminaire or fixture that generally faces downward, and its purpose is to illuminate a space in a room, for example. Conventional waveguide troffers often include a light source, an opaque back cover, a reflector, a waveguide, and a front protector (which may be translucent to diffuse light from the light source, or may be transparent to allow the light from the light source to pass through). The optical system of such waveguide troffers operates to couple the light from the light source (typically one or more light-emitting diodes (LEDs)) into the waveguide. The waveguide has light extraction features that enable a portion of the light to exit the waveguide in a downward direction through the front protector and onto the space to be illuminated. However, the waveguide also directs a portion of the extracted light upward onto the reflector which then reflects that portion of light downward towards the space to be illuminated.
FIG. 1 is an exploded view of a conventional LED-based luminaire 100 that is configured to act as a troffer. One such typical luminaire is known as the LUMINATION™ LED Luminaire (which is available from GE Lighting Solutions, LLC), which produces an even glow and thus delivers exceptionally uniform light to fill a space. Such a luminaire may be configured to fit within a predefined space normally occupied by a ceiling tile within a dropped ceiling, for example, and has a front surface that lies flat or flush with the other ceiling tiles when in place. When not illuminated, such a luminaire may appear to a viewer as being free of a visible light source, and thus may blend in with the ceiling pattern or ceiling tile pattern.
Referring to FIG. 1, the LED-based luminaire 100 includes a light source 102, which generally includes a plurality of edge-lighting LEDs. The LEDs are positioned to be in optical communication with a light guide 104 (for example, a substantially planar waveguide). A reflector 106 is positioned above the light guide 104 and below a backing plate 108 (which may be, for example, an opaque back cover or a metallic plate). Thus, the reflector 106 is sandwiched between backing plate 108 and the light guide 104. A diffuser screen 112 is typically included on the outward-facing or downward-facing side of the LED-based luminaire 100, and operates to mix and/or diffuse the light emitted by the light source 102 and waveguide 104 configuration. Lastly, a trim portion 114 is provided for mechanical support of the various components, and may be designed to provide aesthetic appeal, for example, by matching the frame portions 116 surrounding the ceiling tiles 110.